This invention relates to compositions and methods for inhibiting the deposition of organic contaminants in pulp and papermaking systems. The current method also relates to controlling the deposition of organic contaminants on equipment in the pulp and papermaking systems, which can cause both quality and efficiency problems. Organic contaminants found in pulp and paper systems are diverse mixtures containing pitch, stickies, and papermaking additives. The term “pitch” can be used to refer to deposits composed of organic constituents originated from natural wood resins, such as fatty acids, resin acids, esters of fatty acids, glycerols, sterols, and other fats and waxes. Pitch deposits usually form from microscopic particles of tacky, hydrophobic material in the stock which accumulate on pulp or papermaking equipment. These deposits can be found on, for example, stock chest walls, paper machine foils, machine wires, Uhle boxes, press felts, roll surfaces, dryer felts, dryer cans, and calendar stacks.
Stickies is a term that has been used to describe deposits that occur in systems using recycled fiber. These stickies deposits often contain the same materials found in “pitch” deposits as well as adhesives, hot melts, waxes, inks, binders, coatings, etc. Papermaking additives, such as defoamers, sizing agents, coating binders, solvents, strength agents, fillers, and other additives, are also often found in stickies deposits. These deposits tend to cause many of the same difficulties that pitch deposits can cause. The most severe stickies deposits tend to be found on stock chest walls, paper machine wires, wet felts, roll surfaces, dryer felts, and dryer cans. Either pitch or stickies deposits can impact machine runnability (e.g., reduced production yield) and paper quality (e.g., holes, dirt, sheet defects, inferior converting/printability, etc.).
All of the aforementioned organic materials have many common characteristics including: hydrophobicity, tackiness, deformability, relatively low surface energy, and a tendency to agglomerate. These characteristics contribute pitch and stickies agglomeration and machine deposition. To stabilize these pitch and/or stickies particles in the pulp slurry, one of the methods is to use a chemical to create a stabilization barrier around them. This barrier (i.e., protective layer) renders the particles with higher hydrophilicity and lower tackiness. The modified pitch and/or stickies particles have a less tendency to deposit onto the paper machine surface.
Methods of preventing the build-up of deposits on the pulp and paper mill equipment and surfaces are of great importance to the industry. The paper machines could be shut down for cleaning, but ceasing operation for cleaning is undesirable because of the consequential loss of productivity. Poor paper quality occurs when deposits break off and become incorporated in the sheet. Preventing deposition is thus greatly preferred where it can be effectively practiced. Chemical treatment techniques for organic contaminants control include dispersion, detackification, cationic fixation, wire passivation, and solvent cleaning. These methods, however, are not commonly used together since they may conflict with each other.
In dispersion technology, dispersants such as surfactants and water-soluble polymers, are used to chemically enhance colloidal stability of pitch and stickies particles in pulp. This function allows pitch and stickies to pass through the papermaking process without agglomerating or depositing. Examples of related art include U.S. Pat. Nos. 4,744,865, 5,139,616, 6,051,160, and 6,369,010.
In detackification technology, surface-active water-soluble polymers, surfactants, or inorganic compounds (e.g., talc and bentonite) are used to form a protective layer around the pitch and stickies particle surfaces to reduce their tackiness and depositability. U.S. Pat. Nos. 4,744,865; 4,846,933; 4,871,424; 4,886,575; 5,074,961; 5,266,166; 5,292,403; 5,393,380; 5,536,363; 5,556,510; 5,885,419; 5,723,021; 5,746,888; 5,762,757; 5,779,858; 5,866,618; 5,885,419; 5,952,394; 6,143,800; 6,461,477; and WO 2001/088264 A2, describe the use of water-soluble polymers, surfactants, or inorganic compounds as detackification agents for pitch and stickies control.
Water-soluble polymers are often used for cationic fixation. Examples of water-soluble polymers include polyamines, polyDADMAC, polyacrylamides, polyvinylamines, polyethylenimines, and polyacrylamide polyDADMAC copolymers. These polymers are generally cationic in nature and readily interact with the negatively charged colloidal particles to remove them from the pulp and paper system by “fixation” to the wood fibers in the paper. U.S. Pat. Nos. 4,190,491; 4,710,267; 4,765,867; 5,131,982; 5,393,380; 5,837,100; 5,989,392; and 7,407,561; European Application Nos. EP 464993 and EP 058622, and WO 2000/034581A1 disclose fixation-related technology for contaminants control.
For wire, felt, and dryer fabric passivation, conventional practices include treating machine wire with cationic water-soluble polymers to form a protective layer on wire and felt surfaces. For dryer fabric passivation, a common practice is to apply a chemical treatment that makes a fabric surface more hydrophobic than an untreated surface. This protective layer prevents organic contaminants from deposition. Nonionic water-soluble polymers are also found to be effective in wire and felt passivation applications. The following references are examples of this type of technology: U.S. Pat. Nos. 4,956,051; 4,995,944; 5,223,097; 5,246,548; 5,300,194; 5,368,694; 5,626,720; 5,723,021; 5,762,757; 5,952,394; 6,517,682; and 7,534,324.
Solvent-based cleaning is a common mean to clean organic deposits on paper machine surfaces. Solvents or solvents blended with surfactants are typical materials used for this application. Usually, solvent based cleaning products are not compatible with dispersants, detackifiers, cationic fixatives, or wire passivation agents due to their functionalities and mechanisms. References related to this technology are disclosed in U.S. Pat. Nos. 5,656,177; 5,863,385 and 6,369,010; WO 2012/022451; and European Application Nos. EP 731776 and EP 828889.
Lignin-based Compound: Lignosulfonates
Lignosulfonates are well known pitch dispersants (U.S. Pat. No. 3,398,047). They also can act as emulsion stabilizers. Some advantages are to use lignosulfonates to enhance emulsion stability under salt contamination, mechanical stress, and temperature variations that occur in the typical processes of use. For instance, lignosulfonates are used in a variety of wax/water and oil/water emulsions for applications varying from paper sizing to asphalt stabilization. Another application for lignosulfonates is its use in alkaline or acid industrial cleaners. They function as dispersants for dirt particles, as mild surfactants for improved rinsing, and as complexing agents for metal ions. In water treatment applications, lignosulfonates are used as dispersants and scale-deposit inhibitors in boilers and cooling towers. Spent sulfite liquor containing lignosulfonates and sugar acid salts can also be used to control slime in the paper making process.
Historically, lignosulfonates and other lignin based products have been used in the traditional industries such as oil drilling additives, dust control, concrete additives, asphalt-emulsifying agent, dyestuff dispersants, agricultural chemicals, animal feed, and industrial binders. Advances in lignin technology, however, have led to the development of specialty products that can compete with higher cost synthetics. Examples of these advanced uses include the paper industry, enzyme protection, neutralization of biocides, precious metal recovery aids, and wood preservation. The improved performance of these products together with the fact that they are essentially non-toxic and derived from a renewable resource make them versatile, cost-effective chemicals for today's environmentally conscious consumer.
Commercial lignosulfonates are complex anionic polymers obtained as co-products of wood pulping. They are obtained from spent sulfite pulping liquor or from postsulfonation of kraft (i.e., sulfate) lignins. For some applications, spent sulfite liquors containing crude lignosulfonate are used without further modification. For most specialty applications, however, impurities negatively impact performance and purification and/or modification is required. Purification methods include sugar removal by fermentation or chemical destruction. Ultrafiltration and chemical precipitation are also used commercially to produce high purity lignosulfonates. Chemical modifications include: sulfonation, sulfoalkylation, desulfonation, formulation, oxidation, carboxylation, amination, crosslinking, depolymerization, graft polymerization, and combinations of the above. Chemical modifications are generally performed to enhance the dispersing, complexing, or binding properties of the finished products.
Sodium lignosulfonate and its derivatives can be used for preventing pitch deposition in papermaking systems (U.S. Pat. Nos. 3,398,047 and 4,313,790). Naphthalene sulfonate formaldehyde or lignin sulfonate formaldehyde condensate can be used for controlling stickies and pitch deposition on paper machine surfaces (US Pat. App. 2011/0011546).
Lignin adducts, such as lignosulfonate, lignodicarboxylic acids, oxidized lignin-formaldehyde, sulfomethylated lignin, and methylol hydroxybenzene with sulfonated lignin derivatives, are used as dispersants (U.S. Pat. Nos. 3,956,261; 4,221,708; 4,308,203; 4,326,962; 4,444,562; 4,521,336; 4,551,151; 5,749,926; 5,925,743; 5,972,047; 5,980,589; 7,691,982; 2003/0193554; etc.).
Cyanohydrinated lignosulfonate is used as a corrosion inhibitor (U.S. Pat. No. 3,639,263). Polyoxyalkylene lignin compounds are used as thickeners and flocculants (U.S. Pat. Nos. 3,795,665 and 3,912,706).
Lignin derivatives combined with polyvalent cations (e.g., Ca+2, Mg+2, Al+3, etc.) can be used for scale control in cooling water system (U.S. Pat. No. 3,829,388). Alkali lignosulfonate can be used as an antiskid (U.S. Pat. No. 3,869,309).
Lignin amines are used as flocculants, coagulants, scale inhibitors, corrosion inhibitors, tall oil pitch emulsifiers, retention aids, etc. (U.S. Pat. No. 4,775,744 and 2013/0180927). Lignin-based epoxy resin polymers are used for applications such as fertilizers, ion exchange resins, polyurethane, etc. (U.S. Pat. Nos. 4,918,167, 5,066,790 and 5,102,992).
Sulfonated lignin phenol surfactants are commonly used in oil recovery with surfactant flooding (U.S. Pat. Nos. 5,230,814, 6,100,385 and 6,207,808).
Modified lignin polymers, such as amino-substituted lignin phenols, alkoxy-substituted lignin phenols and alkylated lignosulfonate surfactants, can be used as household cleaning agent or detergent (U.S. Pat. Nos. 6,689,737, 8,075,637, and CN103755972).
Enzyme-catalyzed lignin or lignin sulfonate compounds are used as wood binding agent (U.S. Pat. No. 6,280,855) and water absorbers, coagulants, water softeners, etc. (U.S. Pat. No. 6,593,460).
Lignin derivatives with an aliphatic hydroxyl content less than about 2.35 millimole per gram (mmol/g), are used as antioxidants for thermoplastic polymer, nutritional supplement, animal feed, or functional food (U.S. Pat. Nos. 8,288,460, 8,378,020, 8,426,502, 8,431,635, 8,445,562, 8,696,865 and 8,765,846).
Carboxylated, phosphonated, or nitrated sulphur-free lignin are used together with complexing agents (e.g., polyasparaginate) for slime and deposit control in industrial water processes (US Pat. App. 2003/0156970).
Lignin acetate is used to produce pesticides, herbicides, and plant regulating chemicals for the control release of an agricultural active (U.S. Pat. No. 7,771,749).